title: Homogenous fat suppression for bilateral breast imaging using independent shims.
abstract: OBJECTIVE
  To demonstrate the capability of incorporating independent shims into a dual-band spectral-spatial excitation and to compare fat suppression between standard global shims and independent shims for in vivo bilateral breast imaging at 1.5T.
  
  
  METHODS
  A dual-band spectral-spatial excitation pulse was designed by interleaving two flyback spectral-spatial pulses, playing one during positive gradient lobes and the other during negative gradient lobes. Each slab was enabled to have an independent spatial offset, spectral offset, and slab-phase modulation by modulating radiofrequency phase, and independent linear shims were incorporated by playing extra shim gradients. Phantom experiments were performed to demonstrate the functionality of the pulse, and in vivo experiments were performed for 10 healthy volunteers to compare fat suppression between standard shims and independent shims.
  
  
  RESULTS
  The phantom experiments confirmed that the dual-band pulse can provide independent spectral and spatial offsets and linear shims to the two slabs. Independent shims provided qualitatively more homogeneous fat suppression than standard shims in seven out of 10 subjects, with equivalent fat suppression in two of the other three subjects.
  
  
  CONCLUSIONS
  Incorporating independent shims into the dual-band spectral-spatial excitation can provide homogeneous fat suppression in bilateral breast imaging.
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA; Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Misung
authors.initials: M
authors.lastname: Han
authors.forename: Charles H
authors.initials: CH
authors.lastname: Cunningham
authors.forename: John M
authors.initials: JM
authors.lastname: Pauly
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Daniel
authors.forename: Brian A
authors.initials: BA
authors.lastname: Hargreaves
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000465:Algorithms; D016477:Artifacts; D001940:Breast / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique
keywords: bilateral breast MRI; dual-band spectral-spatial excitation; fat suppression; independent shims